Okay, so “chapter” is perhaps too generous a word for it … but it’s our plan, really!
Yosup and I are slowly going to write our own book for Psychology. But rather than be a traditional textbook, the plan is for it to be written for actual students, about topics that would interest them, and in a voice that they might actually read. Traditional textbooks meet, in our humble opinion, none of those criteria.
In advance of the Nature-Nurture unit, I’ve committed to preparing the materials for students to read and watch in advance of class activities. I began by writing what will be one of the small chapters in our book, this one on twin studies.
It took almost 90-minutes to write a scant 1500 character/ 261 words. As I said, this will be a slow process …
Twin studies eliminate, in the case on monozygotic twins, the genetic variable between cases. If one twin is in the control group and the other is in the experimental group, theoretically the ONLY difference between them will be the independent variable — they would generally eat the same food, get the same exercise, watch the same TV shows, be subject to the same parenting strategies, go to the same school, and any number of other similarities. If, instead of listening to Kidz Bop, one of the twins was given only harmonica music to listen to, any significant difference between the twins in, say, musical aptitude could be attributed to the choice of music.
The basic idea of a twin study was taken to its logical conclusion by Viola Bernard, who persuaded an adoption agency to send five sets of twins and one set of triplets into different families — purposefully breaking up the siblings. These children were then secretly followed by psychologists, studying how their unique environments would result in different outcomes given the similar genetic background of each set of siblings. Neither children nor adoptive parents were told of the children’s origins; none knew that they had siblings. The study was ended in 1980, the records are sealed until 2066, but some of the siblings have since found each other — one or two sets of children may still not know they have a sibling!
In short, twin studies highlight the impact of Nurture since the twins’ genetics are the same (in the case of monozygotic twins, that is).